top pcie slot not working - Sonnet M.2 8x4 Silent Gen4 PCIe Card rich 888 slot

On a 2008 Mac Pro (a.k.a. MacPro3,1), it apparently has 2 PCIe 2.0 slots and 2 PCIe 1.1 slots. While the difference won't prevent any PCIe device from working, it does make a difference for speed.

Yesterday I bought PCIe ethernet card which was not working, probably. I returned it and today I bought 1ghz ethernet PCIe card https://www.alza.sk/tp-link-tg-3468-d309053.htm unplugged PC, then pushed card to PCIe slot, nothing happened.

PCIe x1 is the smallest PCIe slot that is not compatible with mPCIe cards.

My computer will not boot when I put a PCIe card into an x16 slot. My computer will not POST (Power on self test) when I put a PCIe card into an x16 slot.